This invention relates to a method and apparatus for manufacturing rings to a desired contour and radial diameter and, more particularly, to a method and apparatus for guiding the metal ring during its manufacture so as to maintain said ring at predetermined location with respect to a pair of roll forming dies.
Metal rings are used throughout industry in a wide variety of applications. Such rings are particularly useful in the construction of parts for gas turbine engines, including the construction of compressor casings, fan casings, combustor liners, and turbine shrouds. Since high temperature metal alloys used in the construction of these rings are relatively expensive and costly to machine, recent developments in the prior art have resulted in new processes wherein the metal ring is manufactured by rolling an initial annular blank between pairs of roll dies until a final contour and radial diameter are achieved without machining of the part. Generally, the initial annular blank is of substantially the same weight as the final ring, but of substantially lesser radial diameter, and the final ring contour and radial diameter is achieved by squeezing the annular blank between a pair of roll dies along its entire circumference so as to simultaneously expand the ring and form the desired final contour.
Prior art methods have utilized guide rolls for guiding the metal ring during the roll forming process. More specifically, these guide rolls, which do not deform the annular metal blank as do the roll forming dies, are spaced at selected locations along the circumference or periphery of the annular blank and serve to generally locate the metal ring with respect to the rolling dies. However, the roll guides known in the prior art are not sensitive to changes in axial width of the metal ring as it is being rolled into its final contour and radial diameter. The change in axial width of the metal ring during the rolling process may be either an increase in axial width or a decrease in axial width depending upon the final contour to be achieved. In either case, guiding or positioning of the work piece precisely as desired with respect to the roll forming dies cannot be achieved with prior art roll guides. By way of example, if the final width of the metal ring is smaller than the width of the initial annular blank, the prior art roll guides are dimensioned to be slightly larger than the width of the initial annular blank. Hence, during the rolling process, as the width of the initial annular blank decreases the clearance between the annular blank and the roll guides progressively increases such that the annular blank may move substantially within the confines of the roll guide. As the width of the annular blank progressively decreases, undesirable movement of the annular blank within the confines of the roll guide likewise increases and hence accurate positioning of the annular blank during the roll process is not accomplished. Conversely, if the width of the initial annular blank is smaller than the axial width of the final metal ring the width of the guide roll is dimensioned to be slightly larger than the width of the final metal ring. Consequently, in this latter instance, a large gap exists between the initial annular blank and the guide roll whereby the guide rolls are ineffective to precisely position the annular blank with respect to the roll forming dies during the initial stages of the rolling process. In either instance, lack of precise positioning or location of the annular metal blank with respect to the roll forming dies causes instability of the annular blank within the roll forming dies and can result in deformation of the annular blank in a manner incompatible with the final ring configuration to be achieved by roll forming process.